The basic design of the conventional piston internal combustion engine (ICE) has changed little since its inception about 120 years ago. The piston ICE is often referred to as a “heat engine,” because it derives its energy from heat. Steam, gasoline, and diesel fuel all have been used to power this engine. In the 1970's, there was concern over the dwindling supply of non-renewable fossil fuels. This, together with the threat of increasing pollution, sparked an interest in exploring alternate sources of energy. Some improvements have been made in efficiency (power per pound of fuel) as well as attempts to decrease harmful emissions. They have occurred largely due to the application of computers to monitor and control various engine parameters.
By its design, the piston ICE does not allow for continually variable piston stroke or velocity, nor does it accommodate variable intake and exhaust valve timing since these parts are mechanically linked. Due to its design, the power piston is not in a position to impart torque to the crankshaft most of the time. Though not available when basic piston engines were conceived, System Control Computers (SCCs) are commonly used today. Extremely accurate position, pressure and temperature sensors as well as efficient fluid motors and linear actuators and associated electronic controls are “off the shelf” items now. Due to the design of the conventional piston ICE, there are limitations in how much more computers can do to improve this engine.